Scientists Reveal Why Dinosaurs Kept Away From Tropics

For years, paleontologists have wondered why plant-eating dinosaurs steered clear of the equator. Apparently, herbivorous dinosaurs were not fond of the tropics. Available evidence suggests that at least until 30 years after dinos first appeared on Earth, they avoided living at low altitudes. Now a group of scientists led by Jessica Whiteside from University of Southampton in Britain has revealed why herbivorous dinos kept away from tropics.

Harsh climate prevented herbivorous dinosaurs from living in tropics

Dinosaurs first emerged about 230 million years ago during the Late Triassic Period. But only small, carnivorous dinos lived in the tropics. Whiteside’s study suggests that a highly unpredictable hot and dry weather, coupled with extremely high levels of carbon dioxide prevented the giant herbivores from inhabiting the tropics for over 30 million years. Findings of the study were published in the journal Proceedings of the National Academy of Sciences.

Paleontologists said that the climate in the tropics was characterized by extreme droughts in some years and wet seasons in others. Every few years, there were raging wildfires that reached temperatures of more than 600 degrees Celsius. These harsh climatic conditions made it difficult for vegetation to grow and survive. So, Triassic plant-eating dinosaurs could not have survived in the tropics.

CO level in Triassic period was six times higher than current levels

Jessica Whiteside said the conditions at the time would have been similar to the arid western U.S. today. The harsh and fluctuating climate meant that only carnivorous, two-legged dinosaurs like Coelophysis could have survived. Researchers found that the carbon dioxide levels were up to six times higher than that of modern levels, which would have had profound effects on the composition of the ecosystems.

To conduct the study, researchers analyzed rock samples from a number of places around the Upper Triassic Chinle Formation in New Mexico, including the Ghost Ranch, where multiple Triassic dinosaur fossils have been discovered. The rocks were deposited by streams and rivers between 205 and 215 million years ago.

At the time, northern New Mexico was pretty close to the equator at 12°N latitude, which is currently at is at 36°N. It is the same latitude as the southernmost tip of India today.